The overexpression of estrogen receptors in normal breast epithelium may augment estrogen sensitivity and hence the risk of breast cancer.

BACKGROUND: Secondary neoplasms of the thyroid gland (SNTGs) are uncommon, and it is important to recognize them in thyroid fine-needle aspiration biopsy (FNAB). METHODS: The authors report a cohort of 62 SNTGs from 7 institutions in the United States and Europe. Patients were identified retrospectively by searching through medical records of the respective institutions. All initial diagnoses were rendered by FNAB. RESULTS: SNTGs represented 0.16% of all thyroid FNABs and were more frequent among women (ratio of women to men, 1.2:1.0). The mean patient age was of 59 years (range, 7-84 years), the mean tumor size was 3 cm (range, 0.9-7 cm), and the mean interval from diagnosis of the primary tumor was 45 months (range, 0-156 months). Eighty-seven percent of SNTGs were diagnosed as malignant by FNAB, and there was a specific SNTG diagnosis in 93% of patients. Immunocytochemistry and flow cytometry, which were used in 30% of patients, were useful ancillary studies. Adenocarcinomas (n 5 23; 37%) and squamous cell carcinomas (SCCs) (n 5 22; 35.5%) represented the majority of SNTGs, followed by lymphoma (n 5 5; 8%), melanoma (n 5 5; 8%), adenoid cystic carcinoma (n 5 3; 5%), and various sarcomas (n 5 3; 5%). Adenocarcinomas originated from the kidney (n 5 9; 39%), lung (n 5 6; 26%), breast (n 5 5; 22%), and colon (n 5 3; 13%). SCCs originated mostly from the head and neck (n 5 13; 59%), followed by lung (n 5 3; 13%), esophagus (n 5 3; 14%), and unknown primary sites (n 5 3; 14%). CONCLUSIONS:Adenocarcinomas from the kidney, lung, breast, and colon along with SCCs represent the majority of SNTGs. The current results indicate that FNAB is a sensitive and accurate method for diagnosing SNTG; however, diagnostic difficulties can occur. Knowledge of clinical history and the judicious application of ancillary studies can increase the sensitivity and accuracy of FNAB for detecting SNTGs. Cancer (Cancer Cytopathol) 2015;123:19-29. V C 2014 American Cancer Society.KEY WORDS: thyroid; secondary neoplasm; metastasis; renal cell carcinoma; squamous cell carcinoma; adenocarcinoma; lymphoma; adenoid cystic carcinoma; fine-needle aspiration; cytology. INTRODUCTIONSecondary neoplasms of the thyroid gland (SNTGs), representing either metastases or direct extension of tumors from adjacent anatomic structures, are uncommon. Their reported incidence varies substantially, however, ranging from 0.1% to 3% in clinical series. 1-15 They have been reported as incidental findings in autopsy studies [16][17][18] with a frequency of 4.4% to 24% in patients with a known primary cancer or widespread Original Article malignancy in which clinically occult thyroid micrometastases may be detected. 4,[19][20][21][22] In the United States and Europe, the most commonly reported primary tumor resulting in symptomatic SNTG is renal cell carcinoma (RCC), closely followed by carcinomas of the breast, lung, and colon. 5,23-25 Secondary lymphoma, melanoma, sarcoma, and head and neck squamous cell carcinoma (SCC) also account for a significant proportion of SNT...

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FNAs of the parathyroid can be easily confused with that of the thyroid, not only because of the clinical similarity between these two types of lesions but also because of the overlap in cytomorphologic features of the aspirated cells. Although no one single cytomorphologic feature is diagnostic, a combination of cytologic parameters noted earlier should raise the possibility of a parathyroid lesion. Aspirates of parathyroid cysts show acellular water-clear fluid with elevated parathyroid hormone measurements.

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